gscreen -add max velocity and angular velocity INI checks

We never checked for max linear velocity, or default/max angular
velocity for jogging.
soon we should even honour angular settings...
Also quit looking for MAX_LINEAR_VELOCITY in the TRAJ section.
There is no such thing in motion controller
gscreen -add functions to change linuxcnc's mode

now they're all in one place
gscreen config -add metric config and clean up TRAJ section

clean up and remove dubious entries
gscreen config -remove unnessasary sample configs

configs that load Gscreen and AXIS are unneeded
and custom_lathe was not different enough
gscreen config -clean up metric INI and add metric tooltable
gscreen config -add a plain gscreen lathe config

This replaces the one that also loaded AXIS
gscreen -switch to manual mode if jog button pressed

sometimes gscreen was still in MDI mode so jogging wouldn't work.
also switch MDI mode switch call to emc_interface file
so all calls are in the same place
gscreen -have the velocity calculated with units

velocity will be in units per minute.
This works fine for linear units but will be wrong for
angular units when the display is not in native machine units.
AXIS has the same problem. SO for the display to always be right
one must know what type of joint is being jogged. More work to be done.
gscreen -add velocity to the status window

It still will be wrong for angular axis not inn native machine units,
but right now we don't have proper jog rates for them anyways.